Feeding devices for elasticized strips of material adapted for stitching onto a base material are well known. In some applications, a stitching machine is used for stitching elastic strips that are prefolded over circular parts of garments, such as, for example, the waist or leg openings of briefs or panties. A tape feeder is used to feed the elasticized tape to the stitching machine in a controlled manner, such as to selectively and differentially elasticise the circular parts as desired. It will be appreciated however, that the invention is not restricted to stitching circular parts.
There are many known stitching machines in which an elastic strip feeder is mounted such as, for example, the Yamato VF2429S-140S-1/AU20/AEF-1, in which the tape feeder comprises a tensioning mechanism vertically displaced with respect to the bed and the presser foot of the machine. The tensioning mechanism comprises a feed roller driven by a servomotor such as a stepper motor, for example, and a parallel holding roller, the rollers having their axes of rotation in horizontal parallel arrangement. Elasticized tape is fed from a spool vertically above the tensioning mechanism and threaded between the feed roller and the holding roller. The tape is then passed to a horizontal folding device which folds the elastic tape over a portion of the circular part of the workpiece or garment to be stitched together.
The length of elastic strip between the tensioning mechanism and the part of the garment to be stitched is kept in tension. The amount of tension is controlled by altering the rate of feed of the elastic tape through the tensioning mechanism by means of the stepper motor, relative to the rate of feed of the folded elastic strip on the garment at the stitching station. The stepping motor is typically computer controlled. The amount of tension in the tape determines the amount of stretching thereof, and, therefore, the degree of pleating or creasing of the material onto which the tape is stitched once the tension is removed and the tape returns to its unloaded state.
However, this system suffers from a number of problems. For example, as the stepper motor changes speed, the resulting acceleration and deceleration affects the tension in the elastic strip. This change in tension needs to be compensated for, since otherwise the stitch density, and therefore the degree of elastication, (and therefore of pleating or creasing) of each portion of the circular part of the circular garment will be different than desired. Compensation for the varying tension is usually performed manually using an iteration method involving periodically checking the stitch density over a particular tubular component of one garment and performing a correction for the next garment.
Also, the elastic tape is longitudinally folded in two, and downstream thereof the part of the garment to be stitched with the folded elastic strip is horizontally fed to the presser foot at the stitching station. In the aforesaid prior art machines, the elastic tape is vertically fed to the tensioning mechanism and has to be passed through two 90.degree. turns in order to be properly fed to the folding and stitching stations. In order to accommodate these two turns, the distance between the tensioning mechanism and the stitching station has been traditionally large.
Further, maintenance of the tape feeder is difficult due to low accessibility thereto, and typically the whole tape feeder assembly has to be unscrewed and dismounted from the stitching machine. More so, access to the footer zone (e.g. for inserting thread, etc) and maintenance of the presser foot or folding device is even more difficult since these components are blocked by the feeder assembly, which must therefore also be removed from the stitching machine in order to effect such maintenance.
U.S. Pat. No. 5,222,989 to IIyca discloses a tape feeder comprising a motor driven roller and a parallel presser roller. In one mode of operation, these two rollers are brought together and tape pinched therebetween can be advanced to the stitching station and thus acts as a tensioning mechanism. U.S. Pat. No. 5,269,257 to Yamazaki is directed to the problem of the overlapping length of the tape tail end of the sewing front portion. A tape feeder is disclosed as part of the machine described therein. The tape feeder comprises a feed roller rotated by a motor and a holding roller. Tape pinched between these two rollers can be advanced to the stitching station and thus acts as a tensioning mechanism.
U.S. Pat. No. 4,020,776 discloses a vertically fed feeder comprising parallel rollers, and the feeder is carried on a pivotal bracket lockably secured to the base of the stitching machine.
None of these patents addresses the problems raised herein.
It is therefore an aim of the present invention to provide a device that overcomes or substantially reduces the above limitations of prior art tape feeder devices. In particular, it is an object of the present invention to provides a versatile tape feeder that enables the distance between the tensioning mechanism and the stitching station to be substantially reduced and where it may be turned by 90.degree. by a simple operation to enable elastic tape to be fed horizontally or vertically, from a spool. The present invention also comprises means for swinging away the tensioning mechanism from the stitching machine for easy operator access thereto and to the presser foot and folding device.